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BIOCHEMISTRY > Biosynthesis and Cholesterol Synthesis > Flashcards

Biosynthesis and Cholesterol Synthesis Flashcards

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1
Q

What is cholesterol biosynthesis?

A

The process by which cells synthesize cholesterol from simpler molecules.

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2
Q

What is the primary site of cholesterol biosynthesis in the body?

A

The liver.

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3
Q

Which molecule is a key precursor in the cholesterol biosynthesis pathway?

A

Acetyl-CoA.

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4
Q

Fill in the blank: The first step of cholesterol biosynthesis involves the conversion of ______ to HMG-CoA.

A

Acetyl-CoA.

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5
Q

What enzyme catalyzes the conversion of HMG-CoA to mevalonate?

A

HMG-CoA reductase.

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6
Q

True or False: HMG-CoA reductase is a rate-limiting enzyme in cholesterol biosynthesis.

A

True.

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7
Q

What is the role of mevalonate in cholesterol biosynthesis?

A

It is a key intermediate that is further processed to produce cholesterol.

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8
Q

What do statins inhibit in cholesterol biosynthesis?

A

HMG-CoA reductase.

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9
Q

Multiple Choice: Which of the following is NOT a product of cholesterol biosynthesis? A) Steroids B) Bile acids C) Glucose D) Lipoproteins

A

C) Glucose.

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10
Q

How many carbon atoms does cholesterol have?

A

27 carbon atoms.

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11
Q

Fill in the blank: The conversion of squalene to lanosterol is a crucial step in the ______ of cholesterol.

A

Cyclization.

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12
Q

Short Answer: What is the end product of cholesterol biosynthesis?

A

Cholesterol.

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13
Q

True or False: Cholesterol can be converted into steroid hormones.

A

True.

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14
Q

What is the role of LDL in cholesterol metabolism?

A

LDL transports cholesterol to peripheral tissues.

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15
Q

What happens to cholesterol levels when HMG-CoA reductase is inhibited?

A

Cholesterol levels decrease.

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16
Q

Which enzyme is responsible for the esterification of cholesterol?

A

Acyl-CoA:cholesterol acyltransferase (ACAT).

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17
Q

Fill in the blank: Cholesterol undergoes ______ to form bile acids.

A

Oxidation.

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18
Q

Multiple Choice: Which of the following is a function of cholesterol? A) Energy storage B) Membrane fluidity C) Protein synthesis D) Carbohydrate metabolism

A

B) Membrane fluidity.

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19
Q

What is the role of SREBP in cholesterol biosynthesis?

A

SREBP is a transcription factor that regulates genes involved in cholesterol synthesis.

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20
Q

True or False: Cholesterol is hydrophilic.

A

False

cholesterol is hydrophobic.

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21
Q

What is the significance of the mevalonate pathway?

A

It is the metabolic pathway that leads to the synthesis of cholesterol and other isoprenoids.

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22
Q

Short Answer: What type of molecule is cholesterol?

A

A sterol.

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23
Q

Which organelle is primarily involved in cholesterol synthesis?

A

The endoplasmic reticulum.

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24
Q

What are the consequences of excess cholesterol in the body?

A

It can lead to atherosclerosis and cardiovascular diseases.

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25
Multiple Choice: Which of the following statements is true? A) Cholesterol is only obtained through diet B) The body can synthesize cholesterol C) Cholesterol is not necessary for cell membranes D) None of the above
B) The body can synthesize cholesterol.
26
What is the function of bile acids?
They help in the emulsification and absorption of dietary fats.
27
Short Answer: What is the main regulatory mechanism for HMG-CoA reductase?
Feedback inhibition by cholesterol.
28
What is the primary location of fatty acid synthesis in the body?
The liver and adipose tissue.
29
True or False: Fatty acid synthesis occurs in the mitochondria.
False. ## Footnote cytoplasm of liver and fat cells
30
What is the main precursor molecule for fatty acid synthesis?
Acetyl-CoA.
31
Fill in the blank: Fatty acid synthesis primarily occurs in the _______.
cytosol.
32
What are the two primary building blocks used in fatty acid synthesis?
Acetyl-CoA and malonyl-CoA.
33
Which enzyme is responsible for the conversion of acetyl-CoA to malonyl-CoA?
Acetyl-CoA carboxylase.
34
What is the role of NADPH in fatty acid synthesis?
It provides reducing power for the synthesis process.
35
True or False: Fatty acid synthesis is an anabolic process.
True.
36
What is the end product of fatty acid synthesis?
Palmitate (C16:0).
37
Which enzyme complex is involved in the elongation and desaturation of fatty acids?
Fatty acid synthase complex.
38
What is the function of malonyl-CoA in fatty acid synthesis?
It serves as a substrate for the fatty acid synthase complex.
39
Multiple Choice: Which of the following is NOT a product of fatty acid synthesis? A) Palmitate B) Stearate C) Acetyl-CoA D) Oleate
C) Acetyl-CoA.
40
What regulates the activity of acetyl-CoA carboxylase?
Insulin activates it, while glucagon and epinephrine inhibit it.
41
Fill in the blank: The fatty acid synthesis pathway is regulated by the availability of _______.
NADPH and substrates.
42
True or False: Fatty acids can be synthesized from glucose.
True.
43
What is the significance of the fatty acid synthase complex being a multifunctional enzyme?
It allows for the sequential addition of carbon units in one polypeptide chain.
44
Which vitamin is essential for the synthesis of fatty acids?
Vitamin B7 (biotin).
45
What type of fatty acids are synthesized in the liver?
Saturated and monounsaturated fatty acids.
46
What is the role of citrate in fatty acid synthesis?
It transports acetyl-CoA from the mitochondria to the cytosol.
47
Multiple Choice: Which of the following inhibits fatty acid synthesis? A) Insulin B) Glucagon C) Malonyl-CoA D) Citrate
B) Glucagon.
48
What is the role of AMP-activated protein kinase (AMPK) in fatty acid synthesis?
It inhibits fatty acid synthesis when energy levels are low.
49
Fill in the blank: Fatty acid synthesis is carried out in a series of _______ reactions.
condensation.
50
True or False: Fatty acid synthesis and beta-oxidation occur simultaneously in the same cellular compartment.
False.
51
What is the primary energy source for fatty acid synthesis?
ATP.
52
What is the effect of high carbohydrate intake on fatty acid synthesis?
It promotes increased fatty acid synthesis.
53
What metabolic pathway is closely linked to fatty acid synthesis?
Glycolysis.
54
Fill in the blank: The enzyme fatty acid synthase synthesizes fatty acids in a _______ manner.
stepwise.
55
What is the function of the acyl carrier protein (ACP) in fatty acid synthesis?
It holds the growing fatty acid chain during synthesis.
56
Multiple Choice: Which of the following is a product of fatty acid elongation? A) Butyrate B) Palmitate C) Stearate D) All of the above
D) All of the above.
57
True or False: Fatty acids can be synthesized from amino acids.
True.
58
What is the role of desaturases in fatty acid metabolism?
They introduce double bonds into fatty acid chains.
59
Fill in the blank: Fatty acid synthesis requires a constant supply of _______.
NADPH.
60
True or false: cholesterol biosynthesis occurs in the cytosol and the rough ER, but starts in the cytoplasm
false ## Footnote cholesterol biosynthesis occurs in the cytosol and the smooth ER, but starts in the cytoplasm
61
True or false: increased cholesterol results in positive feedback on HMG-CoA reductase
false ## Footnote negative feedback
62
the transition from acetyl CoA to citrate occurs in the _______
cystol
63
the transition from citrate back to acetyl CoA occurs in the _______
cytoplasm
64
True or false: HMG-CoA reductase is active in the rough ER
false ## Footnote smooth ER

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